java - 将 boolean 值设置为 true，但 filewriter 仍然覆盖文件，有什么建议吗？

Question

我创建了一个简单的程序，使用不同的算法对输入文件中的整数进行排序。我还使用 filewriter 将结果输出到另一个文件。不幸的是，无论我如何更改代码，文件都会被覆盖。有什么建议吗？

一直在谷歌上寻找答案，并尝试改变我输入语法的方式，但没有任何效果。

重要部分:

设置编写器

try {

        FileWriter fileWriter = new FileWriter ("Sorted output.txt");

        //BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);

        PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));

输出到文件

 out.println("User's own data set sorted using bubble sort.");
                      out.println(unsortedArray + Arrays.deepToString(FileOne));
                      out.println("Sorted Array looks like this:" + Arrays.toString(intArrayBubble));
                      out.println(timeToSort + bubbleSortIs + bubbleTime + "ms");

它工作得很好，但是它用在 do while 循环中，带有嵌套的 if 语句，并且每个语句都会覆盖另一个语句。

其余代码以防需要 - 已更新 - 仍然无法正常工作

import java.io.*;
import java.util.*;
import java.util.concurrent.TimeUnit;

public class PDD_Sorting {

    public static void main (String [] pArgs) 
    {

        //Array for a file
        String[] FileOne;
        FileOne = new String[0];



        int optionOne = 1,
            optionTwo = 2,
            optionThree = 3,
            secondaryOptionOne = 1,
            secondaryOptionTwo = 2,
            secondaryOptionThree = 3,
            userSelection,
            subUserSelection;

        String     unsortedArray = "Unsorted array is: ",
                   bubbleSort = "Sorted array using bubble sort: ",
                   selectionSort = "Sorted array using selection sort: ",
                   insertionSort = "Sorted array using insertion sort: ",
                   timeToSort = "Time needed to sort this array using ",
                   bubbleSortIs = "bubble sort is ",
                   selectionSortIs = "selection sort is ",
                   insertionSortIs = "insertion sort is ",
                   welcomeToSorter = "Welcome to the SORTER - program that can sort your txt files containing integeres in an ascending order!",
                   notFiles = "Integers, not files :)",
                   pleaseSelect = "Please select one of the following options, by enetering a number asociated with it.",
                   optionOneUserInput = "1. Sort your own data set - input your own set of data (integers, separated by colons, no spaces) into the Input file.",
                   optionTwoPredefined = "2. Use predetermind set of data to test the algorythms.",
                   optionThreeExit = "3. Exit the program.",
                   subMenuPleaseSelect = "Please select which algorythm would you like to use to sort this file.",
                   optionBubble = "(1) - Bubble Sort.",
                   optionSelection = "(2) - Selection Sort.",
                   optionInsertion = "(3) - Insertion Sort.",
                   usersDataBubble = "User's own data set sorted using bubble sort.",
                   sortedArrayLooks = "Sorted Array looks like this:",
                   msTime = "ms",
                   usersDataSelection = "User's own data set sorted using selection sort.",
                   usersDataInsertion = "User's own data set sorted using insertion sort.",
                   validOption = "Please enter a valid option i.e. 1,2 or 3",
                   lessThanZero = "If time shown in ms is 0, that means the time needed to conduct the sort is shorter than 1ms.",
                   fileCreated = "File created.",
                   terminatingProgram = "Terminating the program.",
                   unableToWriteFile = "Unable to write to file";


        System.out.println(welcomeToSorter);
        System.out.println(notFiles);

        Scanner tInput = new Scanner (System.in);

        try {

        FileWriter fileWriter = new FileWriter ("Sorted output.txt");

        //BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);

        PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));

        do {

            System.out.println(pleaseSelect);
            System.out.println(optionOneUserInput);
            System.out.println(optionTwoPredefined);
            System.out.println(optionThreeExit);

        //  Scanner tInput = new Scanner (System.in);
            userSelection = tInput.nextInt();

            if (userSelection == optionOne) {
                //System.out.println("Please enter a valid path for your file.");
                String[] splitFile = null;
                //String userFile = tInput.next();
                FileOne = getAndPrepareFile(splitFile);

                System.out.println(subMenuPleaseSelect);
                System.out.println(optionBubble);
                System.out.println(optionSelection);
                System.out.println(optionInsertion);
                subUserSelection = tInput.nextInt();

                if (subUserSelection == secondaryOptionOne) {
                    int size = FileOne.length;
                      int [] intArrayBubble = new int [size];
                      for(int i=0; i<size; i++) {
                         intArrayBubble[i] = Integer.parseInt(FileOne[i]);
                      }

                      bubbleSort(intArrayBubble);
                      long bubbleTime = timeCount(intArrayBubble);

                      out.println(usersDataBubble);
                      out.println(unsortedArray + Arrays.deepToString(FileOne));
                      out.println(sortedArrayLooks + Arrays.toString(intArrayBubble));
                      out.println(timeToSort + bubbleSortIs + bubbleTime + msTime);



                }

                else if (subUserSelection == secondaryOptionTwo) {
                    int size2 = FileOne.length;
                      int [] intArraySelection = new int [size2];
                      for(int i=0; i<size2; i++) {
                         intArraySelection[i] = Integer.parseInt(FileOne[i]);
                      }

                      doSelectionSort(intArraySelection);   
                      long selectionTime = timeCount(intArraySelection);

                      out.println(usersDataSelection);
                      out.println(unsortedArray + Arrays.deepToString(FileOne));
                      out.println(sortedArrayLooks + Arrays.toString(intArraySelection));
                      out.println(timeToSort + selectionSortIs + selectionTime + msTime);       

                }

                else if (subUserSelection == secondaryOptionThree) {
                     int size3 = FileOne.length;
                      int [] intArrayInsertion = new int [size3];
                      for(int i=0; i<size3; i++) {
                         intArrayInsertion[i] = Integer.parseInt(FileOne[i]);
                      }

                      doInsertionSort(intArrayInsertion);
                      long insertionTime = timeCount(intArrayInsertion);

                      out.println(usersDataInsertion);
                      out.println(unsortedArray + Arrays.deepToString(FileOne));
                      out.println(sortedArrayLooks + Arrays.toString(intArrayInsertion));   
                      out.println(timeToSort + insertionSortIs + insertionTime + msTime);

                }
                else {
                    System.out.println(validOption);
                    tInput.next();
                }

            }

            else if (userSelection == optionTwo){
                //file being prepared and loaded via function
                String[] splitFilePredefined = null;
                FileOne = getAndPrepareFilePredefined(splitFilePredefined);

                //converting string array into int array so the method can sort it.
                int size = FileOne.length;
                  int [] intArrayBubble = new int [size];
                  for(int i=0; i<size; i++) {
                     intArrayBubble[i] = Integer.parseInt(FileOne[i]);
                  }

                  int size2 = FileOne.length;
                  int [] intArraySelection = new int [size2];
                  for(int i=0; i<size2; i++) {
                     intArraySelection[i] = Integer.parseInt(FileOne[i]);
                  }

                  int size3 = FileOne.length;
                  int [] intArrayInsertion = new int [size3];
                  for(int i=0; i<size3; i++) {
                     intArrayInsertion[i] = Integer.parseInt(FileOne[i]);
                  }

                  //inserting pre-prepared int arrays into variables including a timecount method
                    int bubbleTime = timeCount(intArrayBubble);
                    int selectionTime = timeCount(intArraySelection);
                    int insertionTime = timeCount(intArrayInsertion);

                  //sorting array using various sorts
                    bubbleSort(intArrayBubble);
                    doSelectionSort(intArraySelection);     
                    doInsertionSort(intArrayInsertion); 

                    //out.println("Sorted arrray using insertion sort looks like this: " + Arrays.toString(intArrayInsertion));
                    out.println(timeToSort + bubbleSortIs + bubbleTime + "ms");
                    out.println(timeToSort + selectionSortIs + selectionTime + "ms");
                    out.println(timeToSort + insertionSortIs + insertionTime + "ms");
                    out.println(lessThanZero);

                    System.out.println(fileCreated); 

            }

            else if (userSelection == optionThree){
                System.out.println(terminatingProgram);
                System.exit(0);

            }
            else {
                System.out.println(validOption);
                tInput.next();
            }

            out.flush();
            out.close();
            //tInput.close();
        }while (userSelection != optionThree);  


        }

        catch (Exception e)
        {

            System.out.println(unableToWriteFile);
            tInput.next();
        }


        tInput.close();

    }//end main     

    //method that fetches the file from predefined, hardcoded location and removes comas, esentially prepares the file for the next phase
    private static String[] getAndPrepareFile (String[] splitFile)

    {

        Scanner fileIn = null;

        try 
        {

            fileIn = new Scanner(new FileInputStream("C:\\Users\\Greg\\Documents\\Programming\\PDD - Assignment 1\\Input.txt"));

            String fileNew = fileIn.next();

            splitFile = fileNew.split(",");

            //System.err.println(Arrays.toString(splitFile)); //Arrays.toString needed to print the array correctly, otherwise it prints the address of the object

            fileIn.close();


        }
        catch (IOException e)
        {

            System.out.println("File not found.");
            //System.exit(0);
        }
        return splitFile;



    }   
    //as above but works for predefined file, that can be generated using randomNumber.java program
    private static String[] getAndPrepareFilePredefined (String[] splitFilePredefined)
    {

        Scanner fileIn = null;

        try 
        {

            fileIn = new Scanner(new FileInputStream("C:\\Users\\Greg\\Documents\\Programming\\PDD - Assignment 1\\Generated input.txt"));

            String fileNew = fileIn.next();

            splitFilePredefined = fileNew.split(",");

            //System.err.println(Arrays.toString(splitFile)); //Arrays.toString needed to print the array correctly, otherwise it prints the address of the object

            fileIn.close();


        }
        catch (IOException e)
        {

            System.out.println("File not found.");
            //System.exit(0);
        }
        return splitFilePredefined;



    }   
    //method used to sort a file using bubble sort
    private static void bubbleSort(int[] arr) { 


        int n = arr.length;  
        int temp = 0;  
         for(int i=0; i < n; i++){  
                 for(int j=1; j < (n-i); j++){  
                          if(arr[j-1] > arr[j]){  
                                 //swap elements  
                                 temp = arr[j-1];  
                                 arr[j-1] = arr[j];  
                                 arr[j] = temp;  
                         }  

                 }  
         }  

    }  
    //method used to sort a file using selection sort
    private static int[] doSelectionSort(int[] arr){

        for (int i = 0; i < arr.length - 1; i++)
        {
            int index = i;
            for (int j = i + 1; j < arr.length; j++)
                if (arr[j] < arr[index]) 
                    index = j;

            int smallerNumber = arr[index];  
            arr[index] = arr[i];
            arr[i] = smallerNumber;
        }
        return arr;
    }
    //method used to sort a file using sinsertion sort
    private static int[] doInsertionSort(int[] input){

        int temp;
        for (int i = 1; i < input.length; i++) {
            for(int j = i ; j > 0 ; j--){
                if(input[j] < input[j-1]){
                    temp = input[j];
                    input[j] = input[j-1];
                    input[j-1] = temp;
                }
            }
        }
        return input;
    }
    //method used to calculate how much time has lapsed while using any of the given sort methods, outputs in ms, if less than 1 ms, outputs 0ms
    private static int timeCount (int[] anArray)
    {
        long start = System.nanoTime();
        Arrays.sort(anArray);
        long end = System.nanoTime();
        long timeInMillis = TimeUnit.MILLISECONDS.convert(end - start, TimeUnit.NANOSECONDS);
        //System.out.println("Time spend in ms: " + timeInMillis);

        return (int) timeInMillis;

    }

}//end class

文件不断被覆盖，我如何阻止它并使其添加到文件中？

Answer 1

您不需要第一个FileWriter fileWriter = new FileWriter("Sorted output.txt");;这实际上是创建/覆盖文件，之后您的 PrintWriter 再次打开它进行追加。

所以，改变一下

// ... omitting beginning
try {
    FileWriter fileWriter = new FileWriter ("Sorted output.txt");
    //BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);
    PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));
    do { 
// ... omitting rest

至

// ... omitting beginning
try {
    //BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);
    PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));
    do { 
// ... omitting rest